The Hematocrit Test – How and Why It Is Performed

Introduction to the Hematocrit Test:

The hematocrit test determines the percentage of whole blood that is made up of red blood cells (RBCs). A normal hematocrit test result for males is about 45% (38-50%) of blood volume. For females, it is about 40% (35-44%) of blood volume.

The hematocrit test.

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The test results are affected by RBC number, RBC size, and plasma volume. A low test result can be produced by a low number of RBCs, microcytosis (small RBCs), or an increased plasma volume. A high test result can be produced by a high number of RBCs (polycythemia), macrocytosis (enlarged RBCs), or a low plasma volume.

Test Procedures:

First, a finger is lanced and a small drop of blood is allowed to accumulate.